| java.lang.Object
 javax.media.jai.Histogram
| Histogram | | public class Histogram implements Serializable(Code) | | This class represents a histogram accumulated from a
RenderedImage.
A "bin" is a container, where each element stores the total number
of pixel samples of an image whose
values lie within a given range. A histogram of an image consists of
a list of such bins whose range does not overlap with each other
(mutually exclusive). For an image that has multiple samples per
pixel (multi-banded images), a separate list of bins represents each
individual band.
A "low-value" specifies the lowest inclusive pixel value to be
checked, and a "high-value" specifies the highest exclusive pixel
value to be checked. Therefore, the width of a bin
(binWidth) is determined by
(highValue - lowValue) / numberOfBins. The range
of bin i is defined as from
lowValue + i * binWidth inclusive to
lowValue + (i + 1) * binWidth exclusive.
The image may have any data type. Its histogram may be accumulated
over the entire image, or over a specific region-of-interest (ROI)
within the image's bounds. Furthermore, the horizontal and vertical
subsampling factors specify the rate of sampling in the two directions,
so that only every nth pixel will be counted. This allows the
accuracy of the histogram to be traded for the speed of the computation.
Of course a subsampling rate of 1 means every pixel will be counted.
The "Histogram" operator generates the histogram data of an image
and uses this object to store the final pixel counts. The operator
returns an instance of this class when a request is made via the
getProperty method for the "histogram" property. The actual
bins may be obtained by calling the getBins method.
See Also: ROI
See Also: javax.media.jai.operator.HistogramDescriptor |
| Constructor Summary | |
| public | Histogram(int[] numBins, double[] lowValue, double[] highValue)
Constructor.
This constructor should be used when numBins,
lowValue, and/or highValues are
different for each band of the image. | | public | Histogram(int[] numBins, double[] lowValue, double[] highValue, int numBands)
Constructor.
This constructor should be used when numBins,
lowValue, and/or highValues may be
different for each band of the image. | | public | Histogram(int numBins, double lowValue, double highValue, int numBands)
Constructor. |
| Method Summary | |
| public void | clearHistogram()
Resets the values of all bins to zero. | | public void | countPixels(Raster raster, ROI roi, int xStart, int yStart, int xPeriod, int yPeriod)
Accumulates the histogram of the pixels within a specific
region-of-interest (ROI) by counting them based on the
indicated horizontal and vertical sampling period. | | public double | getBinLowValue(int band, int bin)
Returns the lowest inclusive pixel value of a given bin
for a specific band. | | public int | getBinSize(int band, int bin)
Returns the number of pixel samples found in a given bin for a
specific band. | | public synchronized int[][] | getBins()
Returns the array of bands of bins, each bin is the histogram for a
band, i.e., the format of the returned array is
int[bands][bins]. | | public int[] | getBins(int band)
Returns the bins of the histogram for a specific band by reference. | | public double[] | getEntropy()
Returns the entropy of the histogram. | | public Histogram | getGaussianSmoothed(double standardDeviation)
Computes a Gaussian smoothed version of the histogram.
Each band of the histogram is smoothed by discrete convolution
with a kernel approximating a Gaussian impulse response with the
specified standard deviation.
Parameters:
standardDeviation - The standard deviation of the Gaussiansmoothing kernel which must be non-negative or anIllegalArgumentException will be thrown. | | public double[] | getHighValue()
Returns the highest exclusive pixel value checked for all bands. | | public double | getHighValue(int band)
Returns the highest exclusive pixel value checked for a specific band. | | public double[] | getIterativeThreshold()
Calculates the threshold using iterative bisection.
For each band an initial threshold is defined to be the midpoint
of the range of data represented by the histogram. | | public double[] | getLowValue()
Returns the lowest inclusive pixel value checked for all bands. | | public double | getLowValue(int band)
Returns the lowest inclusive pixel value checked for a specific band. | | public double[] | getMaxEntropyThreshold()
Calculates the threshold which maximizes the entropy.
The entropy of a range of gray levels is defined to
be the negation of the sum of products of the probability and
the logarithm thereof over all gray levels in the range. | | public double[] | getMaxVarianceThreshold()
Calculates the threshold which maximizes the ratio of the between-class
variance to the within-class variance for each band. | | public double[] | getMean()
Returns the mean values for all bands of the histogram. | | public double[] | getMinErrorThreshold()
Calculates the threshold which minimizes the probability of error.
For each band the histogram is modeled as the sum of two Gaussian
distributions and the threshold which minimizes the misclassification
error is computed. | | public double[] | getMinFuzzinessThreshold()
Calculates the threshold which minimizes the fuzziness. | | public double[] | getModeThreshold(double power)
Calculates the threshold using the mode method.
The threshold is defined to be the minimum between two peaks.
The first peak is the highest peak in the histogram. | | public double[] | getMoment(int moment, boolean isAbsolute, boolean isCentral)
Returns a specified (absolute) (central) moment of the histogram.
The ith moment in each band is defined to be the mean
of the image pixel values raised to the ith power in that
band. | | public int | getNumBands()
Returns the number of bands of the histogram. | | public int[] | getNumBins()
Returns the number of bins of the histogram for all bands. | | public int | getNumBins(int band)
Returns the number of bins of the histogram for a specific band. | | public double[] | getPTileThreshold(double p)
Calculates the p-tile threshold.
Computes thresholds such that a specified proportion of the sample
values in each band are below the threshold.
Parameters:
p - The proportion of samples in each band which should be belowthe threshold in the band. | | public Histogram | getSmoothed(boolean isWeighted, int k)
Computes a smoothed version of the histogram.
Each band of the histogram is smoothed by averaging over a
moving window of a size specified by the method parameter: if
the value of the parameter is k then the width of the window
is 2*k + 1. | | public double[] | getStandardDeviation()
Returns the standard deviation for all bands of the histogram. | | public int | getSubTotal(int band, int minBin, int maxBin)
Returns the total bin count for the specified sub-range (via "min"
and "max" bin) of the indicated band. | | public int[] | getTotals()
Returns the total bin count over all bins for all bands.
An array which stores the total bin count is kept in this class
and a reference to this array is returned by this method for
performance reasons. |
| Histogram | | public Histogram(int[] numBins, double[] lowValue, double[] highValue)(Code) | | Constructor.
This constructor should be used when numBins,
lowValue, and/or highValues are
different for each band of the image. The length of the arrays
indicates the number of bands the image has, and the three arrays
must have the same length.
Since this constructor has no way of knowing the actual number
of bands of the image, the length of the arrays is not checked
against anything. Therefore, it is very important that the caller
supplies the correct arrays of correct lengths, or errors will occur.
Parameters:
numBins - The number of bins for each band of the image.The length of this array indicates the number of bands forthis histogram.
Parameters:
lowValue - The lowest inclusive pixel value checked foreach band.
Parameters:
highValue - The highest exclusive pixel value checked foreach band.
throws:
IllegalArgumentException - If numBins,lowValue, or highValue isnull.
throws:
IllegalArgumentException - If the array length of the threearguments are not the same, or any array length is 0.
throws:
IllegalArgumentException - If the number of bins for any bandis less than or equal to 0.
throws:
IllegalArgumentException - If the low-value of any band isgreater than or equal to its corresponding high-value. |
| Histogram | | public Histogram(int[] numBins, double[] lowValue, double[] highValue, int numBands)(Code) | | Constructor.
This constructor should be used when numBins,
lowValue, and/or highValues may be
different for each band of the image. The number of bands in the
image is provided explicitly. If any of the arrays provided
has a length which is less than the number of bands, the first
element in that array is used to fill out the array to a length
of numBands.
Parameters:
numBins - The number of bins for each band of the image.
Parameters:
lowValue - The lowest inclusive pixel value checked foreach band.
Parameters:
highValue - The highest exclusive pixel value checked foreach band.
Parameters:
numBands - The number of bands in the image.
throws:
IllegalArgumentException - If numBins,lowValue, or highValue isnull.
throws:
IllegalArgumentException - If any array length is 0.
throws:
IllegalArgumentException - If the number of bins for any bandis less than or equal to 0.
throws:
IllegalArgumentException - If the low-value of any band isgreater than or equal to its corresponding high-value.
throws:
IllegalArgumentException - If numBands is lessthan or equal to 0.
since:
JAI 1.1 |
| Histogram | | public Histogram(int numBins, double lowValue, double highValue, int numBands)(Code) | | Constructor.
The same numBins, lowValue, and
highValue is applied to every band of the image.
Parameters:
numBins - The number of bins for all bands of the image.
Parameters:
lowValue - The lowest inclusive pixel value checked forall bands.
Parameters:
highValue - The highest exclusive pixel value checked forall bands.
Parameters:
numBands - The number of bands of the image.
throws:
IllegalArgumentException - If numBins ornumBands is less than or equal to 0.
throws:
IllegalArgumentException - If lowValueis less than or equal to highValue.
since:
JAI 1.1 |
| clearHistogram | | public void clearHistogram()(Code) | | Resets the values of all bins to zero. If bins has
not been initialized (null), this method does nothing.
|
| countPixels | | public void countPixels(Raster raster, ROI roi, int xStart, int yStart, int xPeriod, int yPeriod)(Code) | | Accumulates the histogram of the pixels within a specific
region-of-interest (ROI) by counting them based on the
indicated horizontal and vertical sampling period. The result
is stored in the bins array and may be obtained
by calling the getBins method.
The ROI specifies the region within which
the pixels are counted. If it is null, the
entire Raster is counted. If it is not
null and does not intersect with the
Raster, then this method returns without changing
the bins.
The set of pixels to be counted may be obtained by
intersecting the grid (xStart + i * xPeriod,
yStart + j * yPeriod); i, j >= 0 with the ROI
and the bounding rectangle of the Raster.
Parameters:
raster - The Raster that contains the pixels to be counted.
Parameters:
roi - The region-of-interest within which the pixels are counted.
Parameters:
xStart - The initial X sample coordinate.
Parameters:
yStart - The initial Y sample coordinate.
Parameters:
xPeriod - The X sampling period.
Parameters:
yPeriod - The Y sampling period.
throws:
IllegalArgumentException - If raster isnull.
throws:
IllegalArgumentException - If the pixels stored in theraster do not have the same number of bands(samples per pixel) as this histogram's bins. |
| getBinLowValue | | public double getBinLowValue(int band, int bin)(Code) | | Returns the lowest inclusive pixel value of a given bin
for a specific band.
Parameters:
band - The index of the band-of-interest.
Parameters:
bin - The index of the bin whose lowValueis to be returned.
throws:
ArrayIndexOutOfBoundsException - If an invalid bandindex is specified. |
| getBinSize | | public int getBinSize(int band, int bin)(Code) | | Returns the number of pixel samples found in a given bin for a
specific band.
Parameters:
band - The index of the band-of-interest.
Parameters:
bin - The index of the bin whose value is to be returned.
throws:
ArrayIndexOutOfBoundsException - If an invalid band orbin index is specified. |
| getBins | | public synchronized int[][] getBins()(Code) | | Returns the array of bands of bins, each bin is the histogram for a
band, i.e., the format of the returned array is
int[bands][bins].
|
| getBins | | public int[] getBins(int band)(Code) | | Returns the bins of the histogram for a specific band by reference.
Parameters:
band - The index of the band whose binsare to be returned.
throws:
ArrayIndexOutOfBoundsException - If an invalid band indexis specified. |
| getEntropy | | public double[] getEntropy()(Code) | | Returns the entropy of the histogram.
The histogram entropy is defined to be the negation of the sum
of the products of the probability associated with each bin with
the base-2 log of the probability.
The entropy of the histogram.
since:
JAI 1.1 |
| getGaussianSmoothed | | public Histogram getGaussianSmoothed(double standardDeviation)(Code) | | Computes a Gaussian smoothed version of the histogram.
Each band of the histogram is smoothed by discrete convolution
with a kernel approximating a Gaussian impulse response with the
specified standard deviation.
Parameters:
standardDeviation - The standard deviation of the Gaussiansmoothing kernel which must be non-negative or anIllegalArgumentException will be thrown. If zero, thehistogram object will be returned with no smoothing applied. A Gaussian smoothed version of the histogram.
since:
JAI 1.1 |
| getHighValue | | public double[] getHighValue()(Code) | | Returns the highest exclusive pixel value checked for all bands.
|
| getHighValue | | public double getHighValue(int band)(Code) | | Returns the highest exclusive pixel value checked for a specific band.
Parameters:
band - The index of the band whose highValueis to be returned.
throws:
ArrayIndexOutOfBoundsException - If an invalid band indexis specified. |
| getIterativeThreshold | | public double[] getIterativeThreshold()(Code) | | Calculates the threshold using iterative bisection.
For each band an initial threshold is defined to be the midpoint
of the range of data represented by the histogram. The mean value is
calculated for each sub-histogram and a new threshold is defined as the
arithmetic mean of the two sub-histogram means. This process is
repeated until the threshold value no longer changes.
The requested thresholds.
since:
JAI 1.1 |
| getLowValue | | public double[] getLowValue()(Code) | | Returns the lowest inclusive pixel value checked for all bands.
|
| getLowValue | | public double getLowValue(int band)(Code) | | Returns the lowest inclusive pixel value checked for a specific band.
Parameters:
band - The index of the band whose lowValueis to be returned.
throws:
ArrayIndexOutOfBoundsException - If an invalid band indexis specified. |
| getMaxEntropyThreshold | | public double[] getMaxEntropyThreshold()(Code) | | Calculates the threshold which maximizes the entropy.
The entropy of a range of gray levels is defined to
be the negation of the sum of products of the probability and
the logarithm thereof over all gray levels in the range. The
maximum entropy threshold is defined to be that value which maximizes
the sum of the entropy of the two ranges which are above and below the
threshold, respectively. This computation is effected for each band.
The requested thresholds.
since:
JAI 1.1 |
| getMaxVarianceThreshold | | public double[] getMaxVarianceThreshold()(Code) | | Calculates the threshold which maximizes the ratio of the between-class
variance to the within-class variance for each band.
The requested thresholds.
since:
JAI 1.1 |
| getMean | | public double[] getMean()(Code) | | Returns the mean values for all bands of the histogram.
since:
JAI 1.1 |
| getMinErrorThreshold | | public double[] getMinErrorThreshold()(Code) | | Calculates the threshold which minimizes the probability of error.
For each band the histogram is modeled as the sum of two Gaussian
distributions and the threshold which minimizes the misclassification
error is computed. If the underlying histogram is unimodal the mean
value of each band will be returned as the threshold.
The bimodality of the histogram for that band will be identically zero.
The requested thresholds.
since:
JAI 1.1 |
| getMinFuzzinessThreshold | | public double[] getMinFuzzinessThreshold()(Code) | | Calculates the threshold which minimizes the fuzziness.
since:
JAI 1.1 |
| getModeThreshold | | public double[] getModeThreshold(double power)(Code) | | Calculates the threshold using the mode method.
The threshold is defined to be the minimum between two peaks.
The first peak is the highest peak in the histogram. The second
peak is the highest peak in the histogram weighted by a specified
power of the distance from the first peak.
Parameters:
power - The exponent of the distance weighting from thefirst peak. The requested thresholds.
since:
JAI 1.1 |
| getMoment | | public double[] getMoment(int moment, boolean isAbsolute, boolean isCentral)(Code) | | Returns a specified (absolute) (central) moment of the histogram.
The ith moment in each band is defined to be the mean
of the image pixel values raised to the ith power in that
band. For central moments the average of the ith power
of the deviation from the mean is used. For absolute moments the
absolute value of the exponentiated term is used.
Note that the mean is the first moment, the average energy the
second central moment, etc.
Parameters:
moment - The moment number or index which must be positive oran IllegalArgumentException will be thrown.
Parameters:
isAbsolute - Whether to calculate the absolute moment.
Parameters:
isCentral - Whether to calculate the central moment. The requested (absolute) (central) moment of the histogram.
since:
JAI 1.1 |
| getNumBands | | public int getNumBands()(Code) | | Returns the number of bands of the histogram.
This value is the same as the number of bands of the
bins, bins.length.
|
| getNumBins | | public int[] getNumBins()(Code) | | Returns the number of bins of the histogram for all bands.
|
| getNumBins | | public int getNumBins(int band)(Code) | | Returns the number of bins of the histogram for a specific band.
Parameters:
band - The index of the band whose numBinsis to be returned.
throws:
ArrayIndexOutOfBoundsException - If an invalid band indexis specified. |
| getPTileThreshold | | public double[] getPTileThreshold(double p)(Code) | | Calculates the p-tile threshold.
Computes thresholds such that a specified proportion of the sample
values in each band are below the threshold.
Parameters:
p - The proportion of samples in each band which should be belowthe threshold in the band. If p is not in the range(0.0, 1.0) an IllegalArgumentException will be thrown. The requested p-tile thresholds.
since:
JAI 1.1 |
| getSmoothed | | public Histogram getSmoothed(boolean isWeighted, int k)(Code) | | Computes a smoothed version of the histogram.
Each band of the histogram is smoothed by averaging over a
moving window of a size specified by the method parameter: if
the value of the parameter is k then the width of the window
is 2*k + 1. If the window runs off the end of the histogram
only those values which intersect the histogram are taken into
consideration. The smoothing may optionally be weighted to favor
the central value using a "triangular" weighting. For example,
for a value of k equal to 2 the central bin would have weight
1/3, the adjacent bins 2/9, and the next adjacent bins 1/9.
Parameters:
isWeighted - Whether bins will be weighted using a triangularweighting scheme favoring bins near the central bin.
Parameters:
k - The smoothing parameter which must be non-negative or anIllegalArgumentException will be thrown. If zero, thehistogram object will be returned with no smoothing applied. A smoothed version of the histogram.
since:
JAI 1.1 |
| getStandardDeviation | | public double[] getStandardDeviation()(Code) | | Returns the standard deviation for all bands of the histogram.
This is a convenience method as the returned values
could be calculated using the first and second moments which
are available via the moment generation function.
The standard deviation values for all bands.
since:
JAI 1.1 |
| getSubTotal | | public int getSubTotal(int band, int minBin, int maxBin)(Code) | | Returns the total bin count for the specified sub-range (via "min"
and "max" bin) of the indicated band. The sub-ragne must fall
within the actual range of the bins.
Parameters:
band - The index of the band-of-interest.
Parameters:
minBin - The minimum bin index to be counted.
Parameters:
maxBin - The maximum bin index to be counted.
throws:
ArrayIndexOutOfBoundsException - If an invalid band indexis specified.
throws:
IllegalArgumentException - If minBin is greater thanmaxBin.
since:
JAI 1.1 |
| getTotals | | public int[] getTotals()(Code) | | Returns the total bin count over all bins for all bands.
An array which stores the total bin count is kept in this class
and a reference to this array is returned by this method for
performance reasons. The elements of the returned array should
not be modified or undefined errors may occur. The array format is
int[numBands].
since:
JAI 1.1 |
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